SAN JOSE -- A 15-year-old boy told investigators that he wrote the word "bomb" on a shoebox-size package and left it on a bus Wednesday -- triggering a response that affected the evening commute for hours -- but the teen didn't give any indication of why he did it.

Passengers on the Valley Transit Authority bus noticed the suspicious package around 5:45 p.m. Wednesday, and notified the driver who in turn summoned authorities. The bus was evacuated, and streets around Monterey Highway and Capitol Expressway were closed as a precaution. Bus lines 66 and 68 were rerouted around the area.

At 8:14 p.m., the Santa Clara County sheriff's bomb squad X-rayed the package and determined it was empty, according to Cardoza.

Information provided to Santa Clara County sheriff's detectives led them to the Morgan Hill teen, who was contacted Thursday.

"He did admit to it, but did not provide any information as to why," sheriff's Sgt. Jose Cardoza said.

The boy was cited for reporting a false bomb or explosive device, a misdemeanor, and released to his parents.

"Roads were blocked off for over two hours," Cardoza said. "A Caltrain was stopped for over two hours. It really impacted people coming home from work."